First thought - check all the fan belts, they'll squeal like a
banshee if overloaded, especially when the radiator fan clutch kicks
into full lock.  Loose, glazed, rock hard...

 Second, pop the belts off and spin all the belt driven accessories
by hand, feel for lumpy or sloppy bearings.   The alternator, water
pump and all idler pulleys should spin freely, the power steering pump
will have resistance even at hand-turn speeds but it should be even
and smooth turning anyway.  They can start going bad and only complain
under load at first.

   --<< Bruce >>--

CAC boots have been a concern on these... the hot side boot at the turbo can
become split or porous and make a "reedy" noise. If you have a positive air
shut off, some of the early adapter boots were prone to early failures.... I
mention this because you speak of high engine loading... which will have
boost levels quite high - and, if the VGT vanes are sticky, it isn't hard to
get into overboost which can lead to further problems.

Seen the odd tensioner that is getting sticky and can't respond to changing
FEAD belt loads quick enough... I vaguely recall a TSB but can't be sure of
my memory... (old timer thing)...... but this shouldn't depend on engine
load.....

Unless you drive a LOT, this should still be covered under the engine
warranty (5 years / 100,000 MILES but there is a $100 deductible...).

Thanks for your input guys...........vehicle is still under
warranty........hubby says let the Ford guys sort it
out................any other comments on the 6.0 liter diesel would be
appreciated tho'

Denise